This invention relates to suspension systems and, more particularly, to a suspension system for heavy duty trucks, trailers and buses which permit the rear axles thereof to track around corners.
Suspension systems are comprised of springs and dampers or "shock absorbers" which attach to and between the body and tires of the vehicle. The suspension system cushions the occupants and cargo in the vehicle from irregularities in the road surface as well as insure the wheels stay in contact with the road to provide adequate grip for accelerating, braking and cornering. One type of spring which is widely used on the rear axle is the multi-leaf spring which is typically semi-elliptical in shape but may also be of substantially planar configuration. The multi-leaf spring is useful since it also provides damping in addition to providing the function of locating the rear axle, holding it in a set position except for allowing vertical motion with respect to the vehicle chassis.
Other types of springs include the air spring and coil spring. In many rear axles of heavy duty trucks and trailers which have multiple rear axles, torque rods are used in combination with any one of the other types of springs mentioned above to maintain the rear axles perpendicular to the vehicle center-line.
The present invention concerns itself with the inability of present day suspension systems to direct the rear axles and their associated rear drive wheels around corners in an efficient manner. On non-articulated trucks, trailers and buses having multiple rear axles ("tandem" for two, "tri-axle" for three, and so forth), the suspension system maintains the drive axles substantially perpendicular with respect to the longitudinal center-line of the vehicle along which the drive shaft lies. The associated drive wheels therefore take corners in a manner which exerts damaging forces between the drive wheels and road surface since they fail to rotate along the line of curvature of the turn. The result is drive wheels which wear out quickly and tear up road surfaces.
Other self-tracking suspensions systems require installation of all new apparatus which are complex in design and expensive to maintain, and lacking in drive stability.
It is therefore a principle object of the present invention to provide a suspension system which permits the rear axles and associated wheels on multiple rear axle vehicles to automatically track into a turn upon cornering which substantially reduces damaging forces between the rear drive wheels and road surface.
It is a further object of the present invention to provide a vehicle suspension system which increases the useful life of rear drive wheels on multiple rear axle vehicles.
It is another object of the present invention to provide a suspension system of the above type which can be easily incorporated into existing vehicle suspension systems with only slight modifications being made to the springs and/or torque rods thereof.
Other objects will in part be obvious and in part appear hereinafter.